High speed fuel injection system

ABSTRACT

Construction of high speed injectors, a special type switch mechanism for synchronizing the operation of the injectors to the angular position of a motor shaft, a unijunction transistor time delay circuit whose base and emitter voltages are varied in response to variations in different parameters, rapid switching bistable control circuits, which control the injection period in one state, damping circuits for the injector, circuits for transferring the electromagnetic energy liberated by current interruption in one injector coil to the next injector coil to be activated, and circuits for regulating a motor driving a generator to correspond to the voltage, current or power output of the latter.

I Umted States Patent 1 1 1 3,710,763 Bassot et al. 1 Jan. 16, 1973 [54]HIGH SPEED FUEL INJECTION [56] References Cited SYSTEM UNITED STATESPATENTS [75] Inventors: Jacques Bassot, Paris; Louis Mon- 2914710 H959 BH 317/151) a 8 fig Etang la ville of 3,158,791 11 1964 Deneen, Jr. et al.317 1s1 x 2,927,567 3/1960 Breeding i ..l23/l 19 [73] Assignee: Societedes Procedes Modernes DIn- 2,950,706 8/1960 Senckel ..l23/32 j fisopmmi, Les Mureaux, 3,000,368 9 1961 Knapp et al. ..123 119 France3,017,873 l/l962 Dietrich ..l23/l 19 [22] Filed: NOV- 10, 19 PrimaryExaminer-Laurence M. Goodridge [2!] App! No 871 670 Attorney-Kenyon &Kenyon Reilley Carr & Chapin Related US. Application Data [57] ABSTRACT[60] Continuation of Ser. No. 816,767, April 16, 1969, Construction Ofhigh Speed injectors, a Special yp abandoned, which is a division ofSer. No, 630,035, switch mechanism for synchronizing the operation ofApril 11, 1967, Pat, No. 3,456,628. the in'ectors to the angular ositionof a motor shaft, a

J P unijunction transistor time delay circuit whose base [30] ForeignApplication Priority Data and emitter voltages are varied in response tovariations in different parameters, rapid switching bistable3pr1l9l3l,9l:666 :rance 2257292 control circuits which control theinjection period in rance 86 30 one state, damping circuits for theinjector, circuits for transferring the electromagnetic energy liberatedby [52] Cl "123/32 317/151; 5 6 current interruption in one injectorcoil to the next in- Int C i 21 3 jector coil to be activated, andcircuits for regulating a c n s s 6 u a a 6 I I l I a a 6 6 a s t u u 6a 6 6 a l a u u a v n a [58] Fleld of Search ..l23/32, 32 E,[wig/331.672, age current or power Output of the Patten 5 Claims, 34Drawing Figures PATENTEDJAH 16 I975 SHEET 03 0F 11 I N VEN TORS JHCQNJGS5966or PATENTEDJAH 16 I973 8. 710.763

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SHEET lOUF 11 INVENTORS (/ACQU6S flfisor y Zoo/s Wav s/7r h yvn 109 701HIGH SPEED FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION issued July22, 1969 in the name of the present applil cants.

The present invention relates to fuel injection systems, and inparticular to fuel injection systems with electronic controls and theinjectors used with said electronic controls.

It is known that use of fuel injection systems instead of carburetorsfor motors with controlled ignition results in a certain number ofadvantages which are based on the greater possibilities for regulationand for adaptation to the particular type of motor. It is thus possibleto lower the fuel consumption, to increase the power, and above all toreduce the percentage of unburned matter in the exhaust gas, especiallythe carbon monoxide. This is of great importance in cities, where theair pollution reaches serious proportions. However, the use ofconventional injection pumps as are known for diesel motors would leadto a very high price since these devices are extremely precise with verytight tolerances.

Attempts have been made to reduce these inconveniences by electroniccontrol systems using monostable multivibrators for electromagneticinjectors. But these devices again present a certain number ofdifficulties as, for example, a veryhigh price and a relatively sluggishoperation. This is because the electromagnetic injectors only allow avery low injection pressure and their response time to electric signalsis so long that it is impossible to provide one injector for eachcylinder in either direct or indirect injection. On the contrary, it isnecessary to provide only one injector for several cylinders, whichinjects during a period which corresponds to the quantity of fuelrequired for all the cylinders. Obviously with such a system one losesalmost all the advantages of the injection system as compared tocarburetors.

SUMMARY OF THE INVENTION The object of this invention is to provide ahigh speed fuel injection system capable of having one controlledinjector for each cylinder.

The system comprises high speed electromagnetic injectors of a' specialconstruction which inject fuel into the respective correspondingcylinders for a time duration corresponding to the duration of aninjection control signal. Distributing means for synchronizing the timeof operation of each of said high speed injectors to a correspondingpredetermined angular position of a motor shaft generate injectionstarting signals corresponding to each of said angular positions. Theseinjection starting signals also serve as inputs to variable delay means,which generate end of injection signals after a time delay varying as afunction of one or more motor or ambient parameters. Bistable controlmeans, which switch from a first to a second state upon receipt of theinjection starting signals, and back to the first state upon receipt ofthe end of injection signals, generate said injection control signalsdetermining the length of the injection period while in said secondstate. These injection control signals are then coupled to the highspeed injectors.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages 0 thereof,will be best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

FIG. 1 is an overall diagram of the fuel injection system;

FIG. 2 is a more detailed diagram of the injection system;

FIG. 3 is a diagram showing a switching mechanism used with theinjection device;

FIG. 4 is an electrical diagram showing the bistable circuit controllingthe injection;

FIG. 5 is a circuit diagram of the delay element of the injectionsystem;

FIG. 6 is an electrical diagram showing the electronic bistable circuitand the delay element;

FIG. 7 is a diagram showing a distributor used with the injectionsystem;

FIG. 8 is a sectional view of the distributor shown in FIG. 7;

FIG. 9 is a curve showing the duration of the injection as a function ofa regulating voltage;

FIG. 10 is an electronic diagram of a manual device for enriching thefuel mixture when the engine is cold, connected with the delay element;

FIG. 11 is an electronic diagram for an automatic device for enrichingthe fuel mixture when the engine is cold, connected with the delayelement;

FIG. 12 is an electronic diagram of an automatic device for enrichingthe fuel mixture when the engine is cold, combined with a device forenriching the fuel mixture as a function of the inlet air temperature;

FIG. 13 is an electronic diagram of a device connected to the gas pedalfor allowing temporary enrichment of the fuel mixture;

FIG. 14 is an electronic diagram of a device for correcting the durationof the injection as a function of the rotational speed of the motor;

FIG. 15 is another embodiment of a device for correcting the duration ofthe injection as a function of the rotational speed of the motor;

FIG. 16 shows a curve showing the duration of injection as a function ofthe speed of rotation with the device shown in FIG. 14;

FIG. 17 is a curve showing the duration of injection as a function ofmotor speed with the device shown in FIG. 15;

FIG. 18 shows another embodiment of a device for correcting the durationof injection as a function of motor speed;

FIG. 19 is a block diagram showing an electronic distributingarrangement device; v

FIG. 20 is a circuit diagram of an arrangement according to FIG. 19;

FIG. 21 is a diagram showing an electronic circuit for protection of thepower transistor;

FIG. 22 is another embodiment of the circuit shown in FIG. 21;

FIG 23 is a first arrangement for the recovery of magnetic energy;

FIG. 24 is a second arrangement for the recovery of magnetic energy;

FIG. 25 is'a third arrangement for the recovery of magnetic energy;

FIG. 26 is a fourth arrangement for the recovery of magnetic energy; I

FIG. 27 is a fifth arrangement for the recovery of magnetic energy;

FIG. 28 shows an arrangement for preventing overvoltages due tointerruption of the injector conti'ol coil current;

FIG. 29 is the arrangement of FIG. 28, combined with an arrangement forthe recovery of magnetic ener- FIG. 30 shows an alternate method forrecovery of magnetic energy;

FIG. 31 shows the current in the injector coil as a I function of time,for the circuit of FIG. 30;

FIG. 32 is a circuit for varying the injection period of a diesel engineas a function of the output voltage of an alternator driven by theengine;

FIG. 33 is a diagram of the circuit for varying the injection period asa function of the power delivered by an alternator driven by the dieselengine; and

FIG. 34 is a schematic diagram illustrating the interconnection ofthecircuits illustrated in FIGS. 6, ll, I2, l3, l4 and 22, providing oneexample of how the injection period for each injector may be controlledas a function of a plurality of motor parameters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, apump 1, driven as described below, has an intake by way of a filter 2either directly from a fuel tank 3 or by way of a feed pump 4, and pumpsthe fuel by way of filter towards the electromagnetic injectors numbered7 to 10. The circuit has a pressure regulating discharge valve 6 and ifnecessary a mechanical or pneumatic back pressure accumulator 1 1.

The electrical and electronic curcuitry is fed by a source of energy,generally the storage battery 13, which itself is connected in aconventional manner to a generator 14 by way of a conventional regulator15. The power may be connected to the electronic curcuitry by switch 16.This switch may be operated independently or it may be connected to theswitch fumishing the power for the motor ignition. The control means 12,receives information regarding the angular position of the motor from adevice 17 and transmits orders in the form of current pulses, to theinjector 7 to by way of the distributor 18, which itself is madedependent on the angular position of the motor by the device 19.

Devices 17 and 18 thus constitute distributing means for synchronizingthe time of operation of each of the high speed injectors to acorresponding predetermined angular position of the crank shaft. Thecontrol device 12 delivers current pulses which have a fixed amplitudeand a width varying linearly with the manifold pressure, through thedistributing means 18 according to a signal furnished by a device 20.The manifold pressure is hereinafter called the fundamental regulatoryparameter.

It should be noted that the particular parameters used for regulation inthe embodiment shown are used purely as illustrative examples and arenot intended to be limiting on the system, since the system is capableof accommodating many other parameters also.

The current pulses furnished by the device 12 undergo, by way of thedevices 21 to 26, corrections 7 based on:

A. The local atmospheric pressure transmitted by device 21 eventuallyincorporated intodevice 20.

B. The motor temperature transmitted by device 22.

C. The temperature of the inlet air transmitted by device 23. j

D. The speed of depression of the pedal controlling the opening of thebutterfly valve, transmitted by device 24. This deviceplaysthe role ofthe acceleration pump in a conventional system having a carburetor.

E. The value of the coefficient of the rate of introduction of air tothe motor, a value which depends on the speed of the motor and on theshape of the manifold. This correction is transmitted by the device 25.

F. The angular lead or lag of the injection which is transmitted by thedevice 26.

As was stated above, the fuel pressure is delivered by the pump 1 whichacts as a simple liquid compressor and has no part in determiningquantities to be furnished. This pressure exists only at the pump andnot in the injectors themselves, which can operate under several hundredbars of pressure (a bar is the international unit of pressure). Foreconomic reasons the operating pressure of the order of ten bars forindirect injectors and of the order of thirty bars in direct injectionsare used. In any case, the pumps used are of con- In a preferredembodiment, the pump 1 is a gear.

pumpdriven by an electric motor and the necessity for the accumulator 11is eliminated. If the electric motor is used it may be energizedautomatically by a switch connected to the system which furnishes thevoltage for T the ignition system.

However, if the pump is driven directly from the motor itself, theaccumulator I 1 is generally necessary. The valve 6 which regulates thepressure may be of a classical pressure regulating type or may be anelectrically controlled valve.

If a pump directly driven by the motor is used, the pressure in the feedpipes of the injectors may drop during a long idle period due to leakageat the valves (6, 28) even though the injectors 7 to 10 are perfectlyliquid tight. In this case, if one wishes to avoid waiting until thepressure has risen sufficiently, when restarting the engine, it ispossible to interpose an electric valve 200 (FIG. 2) between feed pump 4and the injectors 7 to 10. This electric valve is controlled by apressure gauge 201, which by means of a relay box 202, changes theelectric input to the injectors 7 to 10 from the normal electricalsystem to a separate voltage source.

A device 17 (FIG. 1) delivers a pulse at the moment the motor passesthrough a certain number of positions determined in advance, for exampleat the opening of permits the regulation of the advance or retardationof i the fuel injection independent of the advance of the ignition.

' FIG. 3 shows a view of the device. A fixed nonmagnetic disc 601carries one or more switches of the type mentioned above, such as 604,mounted in a cylindrical opening. A second stationary disc 600 similarlycarries one or several permanent magnets such as 605 opposite of theswitches 604. In the absence of a magnetic screen the switches areclosed due to the magnetic field of the magnets. Magnetizable sheets602, connected so as to move with the shaft of a motor, as for examplethe crank shaft, allow a magnetic screen to be placed periodicallybetween the members 604 and 605. By proper choice of the number ofswitches and sheets one may therefore obtain a signal for each cycle ofeach cylinder.

Finally, the turning member is furnished with an advancement device ofknown type operating under centrifugal force.

The current pulse, or injection control signal, delivered by the controlmeans has a duration which is linear with respect to the fundamentalparameter of motor operation, and is modified by other correctionparameters.

According to this invention a bistable control circuit of intermediatepower level is used. The circuit is switched from a first state to asecond state by the injection starting signal generated by device 17,and is flipped back by an end of injection signal whose spacing in timefrom the first signal is determined by information furnished by devicesto 26. Both commands are furnished in the form of switching voltageswhich, in case of an embodiment using transistors, insure a very rapidcommutation.

The bistable circuit is shown in FIG. 4. The transistor controlling theinjector or injectors, 713, (terminals S) is not strictly speaking apart of the bistable circuit.

Starting from a rest condition, an injection starting signal, in form ofa positive pulse, furnished by device 17 is transmitted to the binarycircuit, by the capacitor 700, which will later discharge through diode701. The pulse is transmitted to the base of NPN transistor 705 by diode702 and resistor 704. This voltage injection starting pulse causes veryrapid switching of the transistor, which in turn causes the switching ofPNP transistor 710 by way of resistances 706 and 707 and capacitor 709.This in turn causes control transistor 713 to become saturated.

The bistable circuit is maintained in this second state, during whichinjection takes place, by feeding back a saturation base current fortransistor 705 from the terminal of resistor 714 by means of resistor715. The resistances 703, 707 and 712 maintain the proper voltages atthe bases of the transistors and avoid extraneous flipping due to chargeeffects.

The bistable element is returned to a blocked state by a negative pulseon the base of transistor 705.

The circuit which controls the duration of the injection, FIG. 5, issupplied with a voltage E at terminal 800 and with a voltage V atterminal 801.

The voltage source E charges a capacitor 806 through resistor 802, apotentiometer connected as a rheostat 803, and diode 807.

Transistor 805 is a double base or unijunction transistor. Its firstbase, 810, is connected to ground. The voltage V at terminal 801 issupplied to the second base, 812, through resistor 804. At rest thediode formed by the emitter 811 and base 1, 810, of transistor 805,isnon-conductive. However, it is rapidly energized when the voltage at 811attains a predetermined value:

p=n V82 where 1 is the base-emitter coefficient of transistor 805. iEnergization takes place at a time t such that:

where R the sum of resistors 802 803 and C is the value of capacitor806. Thus:

When transistor 805 is energized, the voltage at terminal 809 changesfrom a zero (ground) value to:

thus polarizing diode 807 in the reverse direction. This negative pulseis used to switch the bistable circuit back to the blocked (or first)state.

The circuit shown in FIG. 5, which is extremely simple, is the variabledelay means which determine the duration of the injection period. Theduration, 1, of the injection thus varies linearly with the value R orC.

The electronic control system 12 therefore becomes that shown in FIG. 6.Transistor 713 (FIG. 4) is omitted here.

As was described above, the variable delay means which determine theduration of the injection period is put into operation at the time ofthe switching of the bistable element by the injection starting pulsederived from device 17 (FIG. 1). After a time proportional to thepressure P the end of the injection signal, namely a negative pulse, istransmitted by resistor 854 to the base of the transistor 705.

The system as shown above has a very great temperature stability. Theprincipal variation is caused by variations in Vp; thus the control iscalculated to yield:

P VA Thus the derivative, for voltage-controlled transistors 705, 710and 713, can only be due to the variations of 1 less than Lt 0.001percent per degree.

The change with temperature per degree is less than FIGS. 7 and 8 show asimple embodiment of distributing means 18 (FIG. 1), using a switchhaving elastic thin lamina if the speed of the motor permits it. Inpractice the device 18 and device 17 are combined and their movableparts are connected to a shaft of the motor, for example the crankshaft.

As shown in FIGS. 7 and 8 such a distributor has four power switches inthe case of a four cylinder motor. These switches have elasticmagnetizable lamina 610 to 613 lodged in the cylindrical cavities of astationary non-magnetic disc 619. Opposite this disc, and a certaindistance removed from it, is a second stationary disc 620 in which smallpermanent magnets 614 to 617 are mounted opposite to each switchinglamina 610 to 613, thus assuring the closing of the switches in theabsence of a magnetic screen between the two discs. The movable part ofthe distributor consists of a magnetic disc 618 having a cutout sector,thus assuring that each of the switches 610 to 613 is closedconsecutively for a period exceeding the maximum duration of injection.

The armature of the device 17 is displaced with respect to the sector ofthe distributor 18 by such an angle that the switch (610 for example) isclosed before the injection signal delivered by it has been transmittedto the control circuit 12.

In this type of operation the distributor itself does not affect theelectric switching at all either in opening or in closing. Furthermore,the switches 610 to 613 are thus able to reach a stable state after thetransients due to rebounds on closing. In addition to thefundamentalparameter determining the injection period, namely the pressure inmanifold 27, it is necessary to provide other corrections to assure thegood functioning of the motor namely:

a. an enriched fuel mixture for starting with a cold engine.

b. a correction as a function of the inlet air temperature.

c. a supplementary injection in case of rapid acceleration.

d. a correction depending on the rate of air admission to the motor,which depends on the rotational speed of the motor.

To facilitate understanding of the arrangement for enriching the fuelmixture for starting with a cold motor, the curve of FIG. 9 may beconsulted, showing the variation of injection duration with regulatingvoltage. The duration of injection is given by:

Therefore if V is increased for starting with a cold motor, willincrease.

Enrichment of the mixture when starting with a cold motor is obtained asshown in FIG. 10. A potentiometer 821 and a fixed resistance 822 form avoltage diregulated automatically with or without additional manualregulation.

FIG. 11 shows the automatic control for this. A voltage divider isformed by resistances 828, 827, and the transistor 823. The voltage. atthe base of the latter is determined by resistors 824, 825 and 826.Voltage V 82 of transistor 805 is thus a function of the collectorcurrent of transistor 823. Here the temperature effect of 'a silicontransistor capable of sustaining relatively high temperatures is used.This transistor, enclosed in a capsule filled with oil, is inserted inthe block of the motor. When the motor warms up, the current in thecollector of transistor 823 increases and voltage V ldiminishes, thusdiminishing the richness of the mixture.

This system is extremely stable and .viable, since transistor 823 is inintimate contact with the water. To limit the enrichment effect to startwith a given water temperature, for example C, a Zener diode 829 may beconnected across the terminals of resistor 828. More simply, resistors824, 825 and 826 may be chosen such that transistor 823.is saturated forthe chosen water temperature. In another embodiment, additionalenrichment may be obtained by insertion of a resistance in series withresistor 803. v

For the correction as a function of air temperature the circuit shown inFIG. 12 may be used, which is analogous to that of the correction withrespect to the water temperature and operates in the same manner.Elements 831, 832, 833, 834 and 835 are so chosen that under normaloperation a correction of the duration of injection of the order of 0.2to 0.3 percent per degree is obtained, which value can be adjusted tothe particular motor used. The air temperature is sensed by transistor830 in exactly the same way as the water temperature is sensed bytransistor 823 as described above.

The device for causing an enriched mixture in case of rapid accelerationis shown in FIG. 13. This circuit comprises a capacitor 836, a resistor837, and a potentiometer 838 connected as shown in FIG. 13.

The slider arm of potentiometer 838 is connected to the acceleratorpedal 29 or the axis of the butterfly valve. At the time of theacceleration the wiper of 838 is displaced toward the left in FIG. 13,thus causing a decrease in the base current of transistor 823 during-avariable time period dependent on the time constant of the circuit 826,836, 837 and 838. This in turn causes the collector current oftransistor 823 to decrease, resulting eventually in the desaturation oftransistor 823 if this device for enrichment when starting the coldmotor has been used, or otherwise in breakdown of the Zener diode 829,resulting in a temporary increase in the voltage V of transistor 805 andtherefore in a temporary enrichment of the mixture. The operation isvaried as a function of the speed of depression of the pedal.

It should be noted that the response time is less than the speed ofpenetration of the air and that therefore there is no sudden drop inrapid acceleration. I

The device for correction as a function rate of admission of air to themotor is necessary because aerodynamic effects in the inlet pipes and,for certain motors, the valve effects in the exhaust and inlet valvesgenerally lead to a decrease in the rate of air intake to the motor athigh speed. Furthermore, because of a resonance effect in the tubing,there usually exists a preferred intake mode, whether this is desired ornot.

FIGS. 14 and 15 show two possible solutions, each using a potentiometerhaving a driven wiper arm. The arm may be driven by a known typetachometric device over the whole speed range or only after a certainthreshold value is exceeded.

In FIG. 14 the potentiometer 839 is of the standard type. In FIG. 15 thepotentiometer 842 has a center tap. FIGS. 16 and 17 show the correctioncurves for the injection time t, as a function of the rotation of speedomega of the motor.

By use of the addition of resistances 843, 844, 845 and 846 almost anydesired shape may be obtained. Box 840' symbolizes the correctionsdiscussed above. However the correction arrangement for motor speed isnot static.

A completely static embodiment of the arrangement is shown in the devicepictured in FIG. 1s.

, When the switch having the elastic lamina (604) FIG. 3 is open,capacitor 851 may charge through diode 850 and resistance 852:

where V is the voltage at capacitor 851; V is the supply voltage of thecircuit, a (alpha) is the angle of rotation in degrees, and w (omega) isthe rotational speed in degrees per second, while I. is definedhereinbelow. At the moment at which switch 604 closes, causing thebeginning of the injection period, the juncture point of 851, 850, 849and 853 rapidly changes to a voltage V,, V Capacitor 851 starts tocharge capacitor 847, and finally discharges through resistor' 853.Capacitor 847 discharges according to an exponential law over members848, 835 and 828 thus producing a change in V,,, (805). This in turnproduces a change in the injection period. By proper coordination of thevarious components, all the correction curves of the type shown in FIGS.16 or 17 may be obtained, since, for a given control pulse:

where A t, is the variation in injection time obtained and t t and B aredefined hereinbelow:

2 C847 (R848 R828 uns) The complete injection arrangement describedabove has, in a first embodiment, a regulatory device, comprising apotentiometer whose wiper arm is controlled by a pressure sensitivearrangement.

FIG. 19 shows a preferred embodiment of the distributor.

The device 17 (FIG. 1) which has been slightly changed and is thereforecalled 1017, sends signals both to the control assembly 12 (FIG. 1)which is also furnished with all the correction arrangements which havealready been described, and to a completely static distributor assembly1001 as shown in FIG. 19. This distributor distributes the controlcurrent pulses to all the injectors. In case of this particular examplethere are 4, corresponding to 4 cylinders, and they are numbered 7 to10.

FIG. 20 shows the electrical schematic diagram. The control device 12includes the main bistable circuitry, the unijunction transistor delaydevice, and the various correction devices described above. The returnto the normal state of the bistable element is controlled mainly by thepressure existing in the tubes, either by use of a potentiometer or byuse of a variable condenser.

In an example of a motor having four cylinders, the device 1017,includes four stationary switches of the type described above numbered1002 to 1005. As shown in FIG. 20 the closure of the switches iseffected by a permanent magnet 1029 which is capable of turning and isconnected to the cam shaft of the motor. Of course the turning membercould also be constituted as was mentioned above by a simple magneticscreen which periodically is placed between each membrane and astationary magnet placed opposite said membrane.

For each closure of switch 1002 to 1005 a positive rectangular signal isproduced which is in turn transmitted by the circuit including diodes1006 to 1009, the resistance 1010, and the input circuit of the controldevice 12 (component 700 and 701) to produce the switching of thebistable control circuit. Switches 1002 to 1005 are connected to thepositive main circuit supply at their common point 1031.

The signals are transmitted independently by the circuits 1012, 1016;1013, 1018; 1014, 1019; 1015, 1020; to the control electrodes of thethyristors 1021 to 1024, each thyristor being connected on the one handto a given switch and on the other hand to the corresponding injector (7to 10).

Interruption of the current in the thyristors and their de-energizationare assured by the blockage of transistor 713.

The latter is protected against overvoltages at the time of currentcutoff by a Zener diode. Generally the assembly of the transistor andthe Zener diode are put together into one housing and the resultantoverall circuitry is designated by the name ignistor hereinafterdesignated by the reference character 713. FIG. 21 shows an alternatemode for protection of the transistor. This consists of placing a diode1032 and a resistance 1033 in parallel with the injector.

Of course, it is also possible to replace the resistors 1025 to 1028 bya single resistance 1028 as shown in FIG. 22.

FIG. 34 illustrates how the circuit of FIG. 22, in one embodiment of theinvention, may be combined with the circuits of FIGS. 6, 11, l2, l3 and14. The portion of the circuit enclosed by the dotted lines at the leftof FIG. 34 represents the circuit of FIG. 6; the central portionenclosed by the dotted lines represents the circuit of FIG. 22; theportion of the circuit enclosed by the dotted lines at the upper rightof FIG. 34 represents a combination of the circuits of FIGS. 11 and 13;the portion of the circuit enclosed by the dotted lines immediatelybelow the last described portion represents the circuit of FIG. 12; andthe portion of the circuit enclosed by the dotted lines immediately tothe left of the last described portion represents the circuit of FIG.14.

The operation of the circuit of FIG. 34 is briefly as follows: Amagnetic switching device which rotates with the crankshaft of themotor, of the type illustrated in FIG. 20 or of the type illustrated inFIGS. 7 and 8, delivers a positive pulse at a predetermined position ofthe crankshaft to capacitor 700 and at the same time delivers such apositive pulse to the control electrode of one of the thyristors 102 1,1022, 1023 or 1024, causing one of said thyristors to become conductive.The particular thyristor which is thus rendered conductive is determinedby the distributor which selects the particular injection coil 7, 8, 9or 10 which is to be energized. 5

ple. The flow of current through coil 7 will continue so long as thebistable multivibrator is in its first state, i.e. with transistor 705conducting. When the bistable multivibrator is switched to its secondstate, transistor 705 cut off and transistor 710 conducting, powertransistor 713 will be rendered non-conductive and the flow of currentthrough coil 7 will cease.

As explained above in connection with FIG. 6, the bistable multivibratorwill remain in its first state for a period of time determined by theseparate variable time delay circuit including variable resistor 803,condenser 806 and unijunction transistor 805. Transistor 705 will berendered non-conductive and transistor 710 will commence conducting whenthe voltage at the collector of unijunction transistor 805, i.e. thevoltage on the condenser 806, is equal to the voltage at the second base(V,,,) of the unijunction transistor 805.

The voltage at the emitter of transistor 805 is determined by the timeconstant of the circuit consisting of resistors 802 and 803 and thecapacitor 806. As described above, resistor 803 is varied in accordancewith manifold pressure. The voltage appearing at the second base ofunijunction transistor 805 is determined by a plurality of other motorparameters and is effected by the combination of the circuits separatelydescribed 4 above in FIGS. 11, 12, 13 and 14, comprising the righthandportion of FIG. 34. This voltage is a resultant of the voltage drops inresistors 828, 835 and 839. The

voltage drop in 828 is determined by the collector current in transistor823 which is a functionof the engine temperature and includes acorrection for engine acceleration in response to-the depression ofaccelerator pedal 29. The voltage drop in resistor 835 is determined bythe collector current in transistor 830 which is a function of airtemperature. The voltage drop in resistor 839 is determined by theposition of its movable wiper arm, which is a function of engine speedand may be driven by any known tachometric device.

Thus, the duration of injection current in each of the injector coils 7,8, 9 and 10 is precisely determined as a function of the manifoldpressure-as well as a number of other motor parameters. Theabove-described cycle of operation is, of course, repeated for each ofthe injector coils.

As was described above, the injectors are opened by an injection controlsignal. There exists a time delay between the moment the voltage isapplied and the moment the injector opens. This delay is caused partlyby the mechanical time constant of the injector and partly by the delayin the current flow in the electric circuit of the injector because ofthe coefficient of self induction of the latter.

Moreover, at the moment the injector is closed, the

magnetic energy which was stored in its magnetic circuit is dissipatedto the exterior in the Joule effect.

Therefore a procedure is proposed which consists in transferring themagnetic energy which is emitted by one injector at the moment of itsclosing to another injector at the moment at which the second injectoropens, in such a manner as to decrease considerably the system to agreater number of cylinders can readily be deduced from the lastdiagram.

Each of the injectors 4007 and 4008 is energized independently by anignistor 713' through a diode 4001 or 4002, respectively, connected to athyristor 4003 or 4004, a diode 4011 or 4012 and a resistance 4013 whilea circuit comprising a diode (4005 or 4006) and a capacitor (4009 or4010)'is connected in parallel with the thyristor-injector branch ofeach circuit.

The operation is described starting with the moment the injector 4007 isopened. The voltage at'its terminals is practically zero. At the momentof cutoff by ignistor 713' there appears across the terminals of 4007 avoltage due to the stored magnetic energy. This is transformed intopotential energy by charging the two capacitors 4009 and 4010, which areconnected in parallel, through the diode 4005. The diode 4005'and thecutoff of the thyristor 4003 blocks the oscillation of the circuitconstituted by the inductance of 4007 and the capacitance 4009 at theend of a quarter cycle.

The two capacitors 4009 and 4010 are now charged to a high voltage. Thisvoltage is positive at the connection with 4011 and negative at theconnection with 4012. This is a stable state.

At the moment of the following injection, that is the conduction ofthyristor 4004, and of saturation of ignistor 7 13', a voltage equal tothe supply voltage appears between the anode of the diode 4002 and thecathode of 4012, while a voltage equal to the voltage across thecapacitors appears'between their other electrodes. l

At the moment that thyristor 4004 is energized, capacitors 4009 and 4010discharge in a quarter of a cyle into the winding of the injector 4008until they are fully discharged. However, when the value of thecondenser voltage reaches the value of the supply voltage a steady-statecurrent is established in the circuit; thus causing an ultra rapidopening of the injector 4008. When this injector is closed thecapacitors are recharged and speed the opening of the injectors 4007 byan identical process.

FIG. 24 shows another version, wherein the resistance 4013 is dividedinto two resistances 4014 and 4015. However the operation of energytransfer of the first embodiment is superior.

FIG. 25 shows an embodiment for a four cylinder motor. This arrangementis preferable to that which would consist simply of combining the twoarrangements for a two-cylinder motor. Particularly with thisarrangement, the value of storage capacity to be used stays the same fora given type of injector, independent of the number of cylinders. Thevalue of capacitance is simply divided into as many elements as thereare cylinders.

Of course, in every case, the establishment of the steady state currenttakes place especially quickly if the transient current resulting fromthe capacitor discharge is permitted to attain the saturation value ofthe magnetic circuit during the opening. It is obvious that thisarrangement is symmetrical for any number of cylinders provided there isno ignition advance. A circuit taking advantage of the symmetry is shownin FIG. 26. The operation of the circuit is identical to that describedin relationship to FIG. 23. Coils 7, 8, 9 and 10 are energized in order.The same total value of storage capacity is used, but a certain numberof diodes is saved. This system may of course be extended to any evennumber of cylinders.

The characteristics of the circuit may be exploited further, (FIG. 27)by replacing the ignistor with a simple thyristor and using theinductance of the injector coils to cause its extinction. Furthermore,the binary symmetry allows use of only two thyristors for initiating theend of the injection period, independent of the number of cylinders. Thearrangement is shown in FIG. 27. Thyristor 4029 controls the extinctionof the main thyristor 4030 when an injector in the odd group is activated, and thyristor 4028 performs the same function for the injectorsin the even group. It should be noted that each time that capacitor4009, for example, charges, capacitor 4009a is also charged via 'diode4005a. At the next cycle, when thyristor 4029 is fired, the positivevoltage on capacitor 4009a appears at the cathode of thyristor 4030 andextinguishes it. This cycle will repeat itself for the firing of theeven number injectors.

An improved circuit for avoiding overvoltages across the switchesserving to control the ignition of the thyristors is shown in FIG. 28.This shows the same circuit as FIG. 20 except that the thyristors 1021,1022, 1023 and 1024 have the cathode connected directly to ground, andthe anode connected to one end of the respective injector coils 7, 8, 9and 10. The other end of the injector coil is connected jointly toresistor 1028 which in turn is connected to the ignistor 713'. Theadvantage of this circuit is as follows. Upon interruption of thecurrent in the injector coils 7 to 10, a high voltage appears acrossthese coils. In FIG. 20 the cathodes of the thyristors are not tied toground, and the gatecathode junction is conductive, permitting a highnegative voltage to be transmitted to the switches having the elasticlamina. If the end of the injection takes place before the opening ofthe corresponding switch this switch is submitted to an unnecessarytransient voltage. Furthermore, if the closing of an injector and theopening of the associated switch happen to coincide, breakdown voltagesmay appear across the switch causing the delay element to produce straypulses. These difficulties are avoided by the arrangement of FIG. 27,where, as mentioned above, the cathodes of all the thyristors areconnected to ground. A corresponding arrangement for a circuit whereintransfer of energy takes place from one injector to the next asdescribed above is shown in FIG. 29.

The circuits illustrated in FIGS. 25-27 above for transferring energyfrom one injector coil to the next have several disadvantages. First ofall, they are only applicable to motors having an even number ofcylinders. Secondly, a relatively high number of diodes is necessary andit is also necessary to have at least two capacitors if one wishes tocharge the capacitors in the same direction each time, thus permittinguse of a relatively cheap component. These difficulties are avoided bythe circuit shown in FIG. 30. The power injection control signal isfurnished by ignistor 713 from a direct current source through aresistor 1028 connected to the anode of diode 5003. The cathode of diode5003 is connected to three series circuits each consisting of athyristor in series with one of the injection coils. The other terminalof each of these series circuits is connected to ground. Connected tothe juncture of diode 5003 and these three series circuits is thecathode of a thyristor 5002, whose anode is connected to the cathode ofa diode 5004 and also by means of capacitance 5001 to the anode of thediode 5003. The anode of diode 5004 is connected to ground. In some ofthese designs the value of resistor 1028 may be zero. Current furnishedby the ignistor 713' is conducted to a chosen injector coil 7, 8 or 9 bya short voltage pulse (injection starting signal) applied to the gate ofthe corresponding thyristor 1023, 1022 or 1021. For this first operatingcycle thyristor 5002 does not serve any particular function. When thecurrent through the particular coil is interrupted at a time determinedby control means 12 the magnetic energy contained in the particular coilis transferred as potential energy to the capacitor 5001 which ischarged in the direction shown in FIG. 30. Capacitor 5001 remainscharged until the following injection takes place. Thyristor 5002 isenergized simultaneously with the next following thyristor correspondingto the next chosen injector. Since diode 5003 is blocked by the voltageon the capacitor 5001, current for the coil is supplied by the dischargecurrent of capacitor 5001. Current may still be furnished to theselected coil by ignistor 713' after the capacitor is discharged andthyristor 5002 is again non-conducting. The operating cycle describedabove is then repeated. FIG. 31 shows the current through any one of theinjector coils as a function of time.

The injection system which is the subject of the present invention mayalso be applied to injectors operating under much higher pressures(several hundred bars) for use in diesel motors. In particular, twotypes of diesel motors would profit from an electromechanical injectionsystem under electronic control, namely, free piston motors and twostroke engines. In the case of free piston motors the injection must bemade at the time when the speed of the moving parts is practically zero.That is, approximately at the dead point. Therefore, an independentinjection system is particularly advantageous. For this type ofapplication the pump is driven by an electric motor as was discussedfurther above (see FIG. 1). The injector, of a size to conform with theparticular motor, is constructed along the lines of the injectordescribed above. Experimental models have functioned up to 350 bars.

Voltage, current, or power regulation may be accomplished for a dynamodriven by an engine by control of the base 2 of transistor 805 (FIG.32). Potentiometer 803 is adjusted for the necessary fuel quantity forfull load functioning. Voltage regulation consists of diminishing thequantity of fuel injected when the load decreases. In the case of a freepiston motor coupled directly to an alternator having a rectangularhysteresis loop, the alternating voltage produced by the generator isapplied to a resistance 870, after rectification by a diode ridge 871and a capacitor 873, and after passing a threshold value set by Zenerdiode 872. Resistance 870 is in the base circuit of unijunctiontransistor 805. When the voltage produced by the alternator exceeds thethreshold voltage of Zener diode 872, the current in resistor 870effectively diminishes the voltage appearing at the base of transistor805 and therefore the quantity of fuel injected.

Current regulation may be accomplished in an analogous manner.

Power regulation is accomplished by starting with potentiometer 803 setto correspond to a no load I power. The circuit used for powerregulation is shown in FIG. 33. A transformer 874, having a centertapped secondary, applies a voltage proportional to the output voltageof the alternator to two pairs of diodes, each pair being connected inparallel and in opposite polarity, namely diodes 878 and 879 and diodes880 and 881 4Arkk'Ul Where it equals the parabolic coefficient of diodes878, 879, 880 and 881; r equals the value of resistors 876 and 877; kequals the no-load transformation ratio of transformer 874; k equals thevoltage to current ratio of current transformer 875; U equals thevoltage delivered by the alternator; and I equals the current deliveredby the alternator. The secondary voltage of transformer 882 is appliedacross the terminals of resistor 870 as shown in FIG. 33, in such a waythat the fuel injection is increased when the power demand increases.

Finally, using conventional methods, one may convert the frequency ofthe alternator to an electrical current and by applying this to resistor870, obtain a frequency regulation.

Without further analysis, the foregoing will so fully respectively. Acurrent transformer 875 delivers a voltreveal the gist of the presentinvention that others can, I

by applying current knowledge, readily adapt it for various applicationswithout omitting features that, from the standpoint of prior art, fairlyconstitute essential characteristics of the generic or specific aspectsof this invention and, therefore, such adaptations should and areintended to be comprehended within the meaning and range of equivalenceof the following claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. In a fuel injection system for internal combustion engines of thetype having a source of voltage; at least a first and a secondelectromagnetic fuel injector, the injectors having, respectively, firstand second injector solenoids connected in parallel across said sourceof voltage; and means connected between'said first and second injectorsolenoids and said source of voltage for selectively applying saidsource of voltage in sequence to said injector solenoids in response toinjector control signals to create injector current pulses forenergizing the injector solenoids in sequence to activate theirrespective injectors to inject fuel into the engine for the duration ofeach corresponding injector control signal, the improvement comprising:7

a. at least one capacitor adapted to be charged in opposite directions;said means for selectively applying said source of voltage in sequenceto said injector solenoids includes first switching means connected inseries with the first injector solenoid and selectively responsive tothe initiation of one of the control pulses for connecting said firstinjector solenoid to said source of voltage and to said capacitor uponinitiation of said one control pulse;

.said means for selectively applying said source of voltage in sequenceto said injector solenoids additionally includes a second switchingmeans connected in series with the second injector solenoid andselectively responsive to the initiation of another of the controlpulses for connecting said second injector solenoid to said source ofvoltage and to said capacitor upon initiation of said other controlpulse;

d. a first diode connected between one terminal of the first injectorsolenoid and one terminal of the capacitor for restricting current flowbetween the first injector solenoid and the capacitor to only a firstdirection;

. a second diode connected between one terminal of the second injectorsolenoid and the other terminal of the capacitor for restricting currentflow between the second injector solenoid and the capacitor to .only asecond direction, opposite to the first direction; v

. a direct connection from the junction between the second diode and thecapacitor to the other terminal of the first injector solenoid; and

. a direct connection from the junction between the first diode and thecapacitor to the other terminal of the second injector solenoid,

whereby said capacitor will be charged in one direction by the electriccurrent generated in said first solenoid upon cutoff of the injectioncurrent pulse that energizes said first solenoid, said capacitordischarging through the second injector solenoid at the instant when asubsequent current pulse is applied thereto so that said second injectorsolenoid is rapidly energized, and said capacitor will be charged in theopposite direction by the electric current generated in said secondsolenoid upon cutoff of the injection control pulse that energizes saidsecond solenoid.

2. A system as set forth in claim 1 and further comprising:

1. In a fuel injection system for internal combustion engines of thetype having a source of voltage; at least a first and a secondelectromagnetic fuel injector, the injectors having, respectively, firstand second injector solenoids connected in parallel across said sourceof voltage; and means connected between said first and second injectorsolenoids and said source of voltage for selectively applying saidsource of voltage in sequence to said injector solenoids in response toinjector control signals to create injector current pulses forenergizing the injector solenoids in sequence to activate theirrespective injectors to inject fuel into the engine for the duration ofeach corresponding injector control signal, the improvement comprising:a. at least one capacitor adapted to be charged in opposite directions;b. said means for selectively applying said source of voltage insequence to said injector solenoids includes first switching meansconnected in series with the first injector solenoid and selectivelyresponsive to the initiation of one of the control pulses for connectingsaid first injector solenoid to said source of voltage and to saidcapacitor upon initiAtion of said one control pulse; c. said means forselectively applying said source of voltage in sequence to said injectorsolenoids additionally includes a second switching means connected inseries with the second injector solenoid and selectively responsive tothe initiation of another of the control pulses for connecting saidsecond injector solenoid to said source of voltage and to said capacitorupon initiation of said other control pulse; d. a first diode connectedbetween one terminal of the first injector solenoid and one terminal ofthe capacitor for restricting current flow between the first injectorsolenoid and the capacitor to only a first direction; e. a second diodeconnected between one terminal of the second injector solenoid and theother terminal of the capacitor for restricting current flow between thesecond injector solenoid and the capacitor to only a second direction,opposite to the first direction; f. a direct connection from thejunction between the second diode and the capacitor to the otherterminal of the first injector solenoid; and g. a direct connection fromthe junction between the first diode and the capacitor to the otherterminal of the second injector solenoid, whereby said capacitor will becharged in one direction by the electric current generated in said firstsolenoid upon cutoff of the injection current pulse that energizes saidfirst solenoid, said capacitor discharging through the second injectorsolenoid at the instant when a subsequent current pulse is appliedthereto so that said second injector solenoid is rapidly energized, andsaid capacitor will be charged in the opposite direction by the electriccurrent generated in said second solenoid upon cutoff of the injectioncontrol pulse that energizes said second solenoid.
 2. A system as setforth in claim 1 and further comprising: a. third and fourth diodesconnected in series between respective terminals of said voltage sourceand the series circuit including the first injector solenoid and thefirst switching means; and b. fifth and sixth diodes connected in seriesbetween respective terminals of said voltage source and the seriescircuit including the second injector solenoid and the second switchingmeans.
 3. A system as set forth in claim 1 wherein said first and secondswitching means comprise first and second thyristors.
 4. A system as setforth in claim 2 wherein the means for selectively applying said sourceof voltage in sequence to said injector solenoids further comprises: anignistor connected between said source of voltage and said third andfifth diodes and responsive to each control pulse for connecting thesource of voltage to said series injector circuits for each period offinite duration and for disconnecting said voltage source from saidinjector circuits at the termination of each of said periods.
 5. Asystem as set forth in claim 3 wherein the means for selectivelyapplying said source of voltage in sequence to said injector solenoidsin sequence further comprises: a. a third thyristor connected betweensaid source of voltage and said third and fifth diodes and responsive toeach control pulse for applying the source of voltage to said seriesinjector circuits upon initiation of each control pulse, said systemfurther including: b. a series circuit comprising a second capacitor anda seventh diode connected between the junction of the first injectorsolenoid and first diode and the junction of the second injectorsolenoid and the second diode, the seventh diode permitting said secondcapacitor to be charged in only one direction; c. a series circuitcomprising a third capacitor and an eighth diode connected in parallelwith the series circuit of said second capacitor and seventh diode, theeighth diode permitting said third capacitor to be charged only in adirection opposite to the charge of the second capacitor; and d. fourthand fifth thyristors for connecting the respective Terminals of likecharge of said second and third capacitors to the junction between thesecond thyristor and the third and fifth diodes in response,respectively, to the termination of said one and the other controlpulses for extinguishing the third thyristor at the end of each controlpulse, thereby disconnecting the source of voltage from the injectorsolenoids and terminating the injector current pulse through theenergized solenoid.